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<h2><span class="refentrytitle">Function template constructor</span></h2>
<p>boost::contract::constructor — Program contracts for constructors. </p>
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<h2 xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" class="refsynopsisdiv-title">Synopsis</h2>
<div xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" class="refsynopsisdiv"><pre class="synopsis"><span class="comment">// In header: &lt;<a class="link" href="../../reference.html#header.boost.contract.constructor_hpp" title="Header &lt;boost/contract/constructor.hpp&gt;">boost/contract/constructor.hpp</a>&gt;

</span>
<span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">typename</span> Class<span class="special">&gt;</span> 
  <a class="link" href="specify__idm45125848167328.html" title="Class template specify_old_postcondition_except">specify_old_postcondition_except</a> <span class="identifier">constructor</span><span class="special">(</span><span class="identifier">Class</span> <span class="special">*</span> obj<span class="special">)</span><span class="special">;</span></pre></div>
<div class="refsect1">
<a name="idm45885987136352"></a><h2>Description</h2>
<p>This is used to specify postconditions, exception guarantees, old value copies at body, and check class invariants for constructors (see  <code class="computeroutput"><code class="computeroutput"><a class="link" href="constructor_precondition.html" title="Class template constructor_precondition">boost::contract::constructor_precondition</a></code></code> to specify preconditions for constructors):</p>
<pre class="programlisting"><span class="keyword">class</span> <span class="identifier">u</span> <span class="special">{</span>
    <span class="keyword">friend</span> <span class="keyword">class</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">contract</span><span class="special">:</span><span class="identifier">access</span><span class="special">;</span>

    <span class="keyword">void</span> <span class="identifier">invariant</span><span class="special">(</span><span class="special">)</span> <span class="keyword">const</span> <span class="special">{</span> <span class="comment">// Optional (as for static and volatile).</span>
        <span class="identifier">BOOST_CONTRACT_ASSERT</span><span class="special">(</span><span class="special">...</span><span class="special">)</span><span class="special">;</span>
        <span class="special">...</span>
    <span class="special">}</span>

<span class="keyword">public</span><span class="special">:</span>
    <span class="identifier">u</span><span class="special">(</span><span class="special">...</span><span class="special">)</span> <span class="special">{</span>
        <span class="identifier">boost</span><span class="special">::</span><span class="identifier">contract</span><span class="special">::</span><span class="identifier">old_ptr</span><span class="special">&lt;</span><span class="identifier">old_type</span><span class="special">&gt;</span> <span class="identifier">old_var</span><span class="special">;</span>
        <span class="identifier">boost</span><span class="special">::</span><span class="identifier">contract</span><span class="special">::</span><span class="identifier">check</span> <span class="identifier">c</span> <span class="special">=</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">contract</span><span class="special">::</span><span class="identifier">constructor</span><span class="special">(</span><span class="keyword">this</span><span class="special">)</span>
            <span class="comment">// No `.precondition` (use `constructor_precondition` instead).</span>
            <span class="special">.</span><span class="identifier">old</span><span class="special">(</span><span class="special">[</span><span class="special">&amp;</span><span class="special">]</span> <span class="special">{</span> <span class="comment">// Optional.</span>
                <span class="identifier">old_var</span> <span class="special">=</span> <span class="identifier">BOOST_CONTRACT_OLDOF</span><span class="special">(</span><span class="identifier">old_expr</span><span class="special">)</span><span class="special">;</span>
                <span class="special">...</span>
            <span class="special">}</span><span class="special">)</span>
            <span class="special">.</span><span class="identifier">postcondition</span><span class="special">(</span><span class="special">[</span><span class="special">&amp;</span><span class="special">]</span> <span class="special">{</span> <span class="comment">// Optional.</span>
                <span class="identifier">BOOST_CONTRACT_ASSERT</span><span class="special">(</span><span class="special">...</span><span class="special">)</span><span class="special">;</span>
                <span class="special">...</span>
            <span class="special">}</span><span class="special">)</span>
            <span class="special">.</span><span class="identifier">except</span><span class="special">(</span><span class="special">[</span><span class="special">&amp;</span><span class="special">]</span> <span class="special">{</span> <span class="comment">// Optional.</span>
                <span class="identifier">BOOST_CONTRACT_ASSERT</span><span class="special">(</span><span class="special">...</span><span class="special">)</span><span class="special">;</span>
                <span class="special">...</span>
            <span class="special">}</span><span class="special">)</span>
        <span class="special">;</span>

        <span class="special">...</span> <span class="comment">// Constructor body.</span>
    <span class="special">}</span>

    <span class="special">...</span>
<span class="special">}</span><span class="special">;</span>
</pre>
<p>For optimization, this can be omitted for constructors that do not have postconditions and exception guarantees, within classes that have no invariants.</p>
<p><span class="bold"><strong>See Also:</strong></span></p>
<p> <a class="link" href="../../boost_contract/tutorial.html#boost_contract.tutorial.constructors" title="Constructors"> Constructors</a></p>
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<td><p><span class="term">Parameters:</span></p></td>
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<td><p><span class="term"><code class="computeroutput">obj</code></span></p></td>
<td><p>The object <code class="computeroutput">this</code> from the scope of the enclosing constructor declaring the contract. (Constructors check all class invariants, including static and volatile invariants, see <a class="link" href="../../boost_contract/tutorial.html#boost_contract.tutorial.class_invariants" title="Class Invariants">
            Class Invariants</a> and  <a class="link" href="../../boost_contract/extras.html#boost_contract.extras.volatile_public_functions" title="Volatile Public Functions">
            Volatile Public Functions</a>).</p></td>
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<td><p><span class="term">Template Parameters:</span></p></td>
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<td><p><span class="term"><code class="computeroutput">Class</code></span></p></td>
<td><p>The type of the class containing the constructor declaring the contract. (Usually this template parameter is automatically deduced by C++ and it does not need to be explicitly specified by programmers.)</p></td>
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<td><p><span class="term">Returns:</span></p></td>
<td><p>The result of this function must be assigned to a variable of type  <code class="computeroutput"><a class="link" href="check.html" title="Class check">boost::contract::check</a></code> declared explicitly (i.e., without using C++11 <code class="computeroutput">auto</code> declarations) and locally just before the code of the constructor body (otherwise this library will generate a run-time error, see <code class="computeroutput"><a class="link" href="../../BOOST_CO_idm45125848615536.html" title="Macro BOOST_CONTRACT_ON_MISSING_CHECK_DECL">BOOST_CONTRACT_ON_MISSING_CHECK_DECL</a></code>). </p></td>
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